No agreement has been reached yet between major world powers and Iran on the future of its nuclear program, Secretary of State John Kerry said Friday.

“There are still some things on the table that are unresolved,” he told reporters in Geneva, BBC reports. “[We] hope to try to narrow the differences but no one should mistake that there are important gaps to be closed.”

Kerry arrived in Geneva on Friday for negotiations with his European and Iranian counterparts at the invitation of Catherine Ashton, the European Union’s top diplomat. The newest round of talks aimed at the long-elusive deal is centered around the possibility of Iran curbing some of its nuclear activities in return for relief from crippling economic sanctions. Kerry was joined by representatives from France, Germany and the U.K. after officials suggested Thursday that an agreement could be imminent; Russian Foreign Minister Sergei Lavrov is expected to join the talks on Saturday.

“We are making progress, but it’s tough,” said Javad Zarif, Iran’s foreign minister, the New York Timesreports.

Before meeting with Kerry in Jerusalem earlier Friday, Israeli Prime Minister Benjamin Netanyahu said his country “utterly rejects” the emerging deal.

“Iran got the deal of the century and the international community got a bad deal,” he said. “I urge Secretary Kerry not to rush to sign, to wait, to reconsider, to get a good deal.”

As reports of a potential agreement spread, Rep. Eliot Engel of New York, the senior Democratic member of the House Foreign Affairs Committee, issued a statement that he was “deeply troubled” that an interim deal might not require Iran to halt its enrichment activities. “I forcefully reject any notion that Iran has a ‘right’ to enrichment, a view which the Administration has publicly articulated on numerous occasions.”

The State Department confirmed Friday that Kerry has postponed his planned visit to North Africa next week after flying to Geneva. “We value our strong relationships with Algeria and Morocco and Secretary Kerry looks forward to leading the U.S. delegations to Strategic Dialogues in those countries in the future,” spokeswoman Jen Psaki said in a statement. He will return to his Middle East schedule after Geneva.